1. Field of the Invention
The present invention is related to navigational systems for vessels and flight vehicles and, more particularly, to a navigational apparatus for using satellite positional signals to determine pitch, azimuth, and position.
2. Description of the Prior Art
It is known in the art to utilize a redundant set of north-seeking gyroscopes to determine the pitch and the heading, or azimuth, of a ship or aircraft. The function of the gyroscopes is to provide to a vessel, for example, an uninterrupted and continuously-smooth attitude reading to be used as an input to a rudder control loop and to the orientation function of a radar image.
A set of two heading sensors is usually specified for most marine navigation. For vessels larger than 500 tons, there is a requirement that at least one of the heading sensors be certified by the International Marine Organization (IMO). This certification ensures that the navigation equipment meets reliability requirements. For these large vessels, the heading sensors must provide continuous heading, that is, there must be no significant heading outage under any circumstances. In addition, if the heading is linked to the auto-pilot or radar, the heading system must ensure that there are no rapid heading changes and the system must not output a heading that indicates a heading change opposite to the actual change in direction of the vessel.
Gyrocompasses are typically used as the heading sensors. The cost of satisfying IMO requirements with a pair of gyrocompasses is about $200,000. While the use of gyrocompasses has proven to be reliable and has become the standard for shipboard navigation, the use of satellite positional signals in conjunction with a magnetic sensor can provide a low-cost and reliable alternative to at least one of the gyrocompass pair.
While the art describes GPS systems used for determining position, azimuth, and pitch of a vessel or flight vehicle, there remains a need for improvements that offer advantages and capabilities not found in presently available devices, and it is a primary object of this invention to provide such improvements.
It is another object of the invention to provide a relatively inexpensive method and apparatus for obtaining position, azimuth, and pitch readings.
Other objects of the invention will be obvious, in part, and, in part, will become apparent when reading the detailed description to follow.